1. Field of the Invention
The present invention relates to crystals of phenylalanine derivatives that have the specific structural formula. The present method also relates to methods for making such crystals.
2. Discussion of the Background
Compounds of the following formula (I) (hereinafter referred to as compound (I)) or pharmaceutically acceptable salts thereof exhibit α4 integrin inhibiting activity and are useful as agents for treating inflammatory bowel diseases and the like. Though they can be produced in accordance with the description of WO02/16329, there is no disclosure of any “crystals” of compound (I) or pharmaceutically acceptable salts thereof in the publication.
Generally, when preserving drug substances or processing or preserving preparations, amorphous or noncrystalline solid drug substances are unstable in the environmental conditions such as temperature, humidity, air, and the like. Therefore, amorphous or noncrystalline solid drug substances can be problematic in developing highly-pure pharmaceutical compositions. Further, since amorphous or noncrystalline solid drug substances are degradable by moisture absorption, the solvents that can be used in processing preparations are limited to those which are anhydrous and, therefore, it can cause an increase in preparation costs. In addition, the drug substances have to be those that can be produced on the industrial scale.